a. Field of the Invention
The instant invention relates to a coupler assembly for catheters having force-sensing capabilities. The instant invention includes a mechanical coupler for coupling a catheter shaft and distal tip sensing components. Such a system may be used with catheters for visualization, mapping, ablation, and/or other methods of diagnosis and treatment of tissue. The instant invention also relates to a method for using a mechanical coupler to couple a catheter shaft and distal tip components, for medical or non-medical purposes.
b. Background Art
The visualization and treatment of organs and tissues has been advanced through the increasing use of catheter systems. Catheter systems have been designed for the incorporation of various components to treat and diagnose ailments, as accomplished through the mapping of organs, sensing of thermal and electrical changes exhibited by a tissue (e.g., heart), as well as the application of energizing sources (such as radiofrequency, cryogenics, laser, and high frequency ultrasound) to tissue.
Catheter systems generally include a portion that contacts the tissue or organ, or is inserted in an environment (e.g., heart chamber or vessel) to detect a number of parameters, such as for example, location of the tissue, contact or pressure exerted on the tissue, electrophysiological attributes of the tissue, or other type of parameters that aid in the evaluation or treatment of the organ or tissue.
It is known that sufficient contact between a catheter, in particular an electrode provided in connection with a catheter, and tissue during a procedure is generally necessary to ensure that the procedures are effective and safe. Current techniques of mapping, visualization and treatment using energizing sources, such as the use of radiofrequency energy during ablation, rely on placing of the electrode (or another component) of a catheter system in consistent mechanical contact with targeted tissue. Perforation of the cardiac wall as well as lesion formation (such as lesions created by exposure to radiofrequency) partially depends upon the direction of contact between the electrode and tissue. In particular, for endocardial catheter applications, the point of electrode-tissue contact is typically 150 cm away from the point of application of force applied by the operator (whether manual or automated) of the catheter outside of the body. Coupled with the fact that a beating heart is a dynamically moving wall, this gives rise to some functional and theoretical challenges such as ensuring that the electrode is in sufficiently constant mechanical contact with the myocardial wall.
Catheter systems having sensor assemblies, such as those mounted on the catheter shaft proximal to the electrode (or another component) or remotely in the handle set, leave the possibility, however small, of obtaining false positive outcomes when detecting contact between the electrode and the tissue. False positive outcomes may occur, for example, when the distal portion of the catheter, and not the electrode, is in contact with the tissue. Such condition may arise during the catheter manipulation in the heart when, for instance, the distal portion of the catheter is curled inward so much as to lose electrode contact with the tissue, while the distal portion of the catheter is in contact with the tissue. When that happens, remotely placed sensors can generate signals due to the deflection of the catheter shaft, thereby falsely indicating contact between the electrode and tissue. Accordingly, contact sensors coupled to the electrode and provided in the distal tip of the catheter can, among other things, help reduce the possibility of obtaining false positive outcomes when detecting contact between the electrode (or another component) and the tissue.
Force sensor configurations that address the foregoing issues have been previously disclosed. In some embodiments, such force sensors include a coupler that couples the electrode with the catheter shaft. In those cases, the sensitivity and the dynamic range of the force sensor depend upon the stiffness of the coupler. Furthermore, the sensitivity and the dynamic range depends upon the directional stiffness of the coupler range of the force sensor because force is a vector (i.e. force has a magnitude and direction). Thus, for example, if the coupler is stiffer in the axial direction than in the transverse direction, the force sensor will have a wider dynamic range in the axial direction than in the transverse direction, and will be more sensitive in the transverse direction than in the axial direction.